Wayne Parham Messages: 18756 Registered: January 2001
Illuminati (33rd Degree)
The box size was just a function of the tuning. You're right that the four Pi is a smidge smaller, but they're really very similar loudspeakers. The three Pi has 3dB lower voltage sensitivity, with exception of the Delta Pro 12 variant, which trades some extension for sensitivity. In all other cases, they have generally similar response with 3dB sensitivity difference.